SYMBIOS

eco-tecture + design + build

living roofs

Living Roofs

Symbios Living Roof FAQ


1. Are green roofs and living roofs the same thing?

2. Are living roofs like landscapes on the ground but on top of buildings?

3. When should one start planning a living roof?

4. At what point in a construction project should one install a living roof?

5. Can one green roof system work for all types of conditions?

6. What is the most important thing to consider with living roofs?

7. Are some waterproof roof membranes better than others?

8. Are all rooftop soil mixes the same?

9. How does one decide on the type of planting scheme?

10. Is there a difference between modular systems & planted in place systems?

11. What do these systems cost?

12. Does the roof need an irrigation system?

13. What is a GRP?

14. What are the main benefits of hiring SYMBIOS?



1. Are green roofs and living roofs the same thing?

The terms are frequently interchangeable and are used to mean the same thing. However, we prefer to use the term living roofs, as the term green roofs may not always imply a living vegetative surface. Green roofs may indicate a roofing material that is providing some type of environmental or building performance improvement, e.g., cool roofs or metal roofs for rainwater catchment, etc.


2. Are living roofs like landscapes on the ground but on top of buildings?

The vegetation of a living roof creates a false appearance of a ground-based landscape.  However, living roofs are primarily a building system and secondarily a landscape feature.

Living roof components and their assembly need to be viewed as any other construction system composing the building. Think in terms of a living roof as a ‘Vegetative Building System.’ This will help set the proper perspective for manifesting any green roof project.


3. When should one start planning a living roof?

Successful living roofs have one common root - careful planning and smart design.  Without reservation, the earlier the pre-design or project conception phase a living roof is addressed, the better its ultimate success.

SYMBIOS offers consultation services for the pre-design period that are available for architectural & landscape firms, as well as developers and property owners alike.


4. At what point in a construction project should one install a living roof?

Many people immediately assume that a living roof needs to be installed at the very end of a building project, much like a landscape on the ground. This is usually not the case. Because living roofs are a building system, they can and should be integrated into the construction process of the buildings envelope to be most effective.

The roofs waterproofing, flashing and drainage components all need to be integrated during the build out phase with the living roof system. In addition, the composite system of a living roof once installed, protects the roof membrane from damage and degradation and should be installed as soon as possible after the waterproofing membrane is completed.

Although, it may be advisable to hold-off planting or seeding until most of the exterior work of the building is complete. All other components can be installed well in advance of this point.


5. Can one green roof system work for all types of conditions?

It is highly unlikely that any one green roof system will be appropriate for all different types of roof conditions, such as slope, site orientation, micro-climate conditions, drainage, etc. Each roof is unique and needs to have the green roof components specified in accordance with the site-specific conditions of the buildings design features as well as the micro-climatic conditions of the roofs location on the building.

At SYMBIOS, we frequently specify the best features of several different products and combine them together to produce high performance systems designed for the long term.


6. What is the most important thing to consider with living roofs?

The correct answer is every aspect from waterproofing through the selection of the flower colors. In addition, addressing the structural loading capacities of the building is paramount. Buildings in active seismic or high wind zones require additional consideration when it comes to adding additional weight of vegetation, soil and water.

This is true for new construction and even more critical for existing structures that are being re-adapted. It cannot be over emphasized that assessing the weight bearing and lateral forces acting upon a structure is a critical dimension of any living roof project being developed.

At SYMBIOS we work with engineering associates that have the professional capacities to conduct the analysis.


7. Are some waterproof roof membranes better than others?

Green roofs may appear ‘green’ by virtue of being alive; they may not always ‘green’ by design. Some roof membranes, although very effective as a waterproof layer, may be composed of synthetic compounds known to be toxic when manufactured or disposed of in the environment. At SYMBIOS, our product resources include eco-effective waterproofing systems that are non-toxic, water-based and LEED approved materials.

Our installation experience on roofs has revealed the most effective systems. We also offer pre-construction design consultation and design service to assist architects and developers with waterproofing specifications.


8. Are all rooftop soil mixes the same?

Rooftop soil mixes all share one common property - to be lightweight. But this is where the difference ends. Soil mixtures need to be tailored to the planting scheme to achieve a viable and productive rooftop landscape. Secondly, manufactured engineered soil mixes for roofs vary in composition of organic and inorganic constituents and thereby have different water holding capacities and weight bearing factors, etc.

At SYMBIOS, we will specify the right soil mix for the job. It is also our preference to use our own soil mix that is a blend we specify using regional materials when the project is based in northern California. We also take care to amend our soil mix with supportive organic ingredients that provide us with a totally organic soil roof mixture.


9. How does one decide on the type of planting scheme?

It is critical to identify the type of planting scheme you want to establish in your rooftop garden at the beginning of your planning process. This decision informs the rest of the design process from soil depth, through the living roof components to the irrigation scheme.

Frequently, the design goals are defined regarding the intention for the future rooftop. Some of these goals may be for ecological reasons due to habitat loss or improving air quality by processing pollution. Storm water management, optimizing building performance or improving the visual aesthetics of a rooftop may also be design considerations. The main design criteria will inform the process of selecting the best planting scheme to optimizes those goals. Visit our roofscape section for more information.


10. Is there a difference between modular systems & planted in place systems (aka field applied)?

Yes. Although modular systems have some appropriate applications, when it comes to greening up roofs, we find the performance of field-applied (planted-in-place) systems are superior as they operate as a whole-integrated system.

For instance, in field applied living roof systems, rainwater moves through the soil to the root systems of the plants as one whole system unlike modular systems that have hundreds or thousands of individualized containers. Also, the sub-soil fauna ecologies that develop are more healthy and dynamic and again are an integral system.  From our experience, the field applied approach produces a more sustainable system requiring less maintenance, watering needs and less replacement of plants.

From our experience, modular systems are surprisingly more expensive upon complete installation then planted-in place systems. In addition, modular systems require more containers and that equates to more resources per given system.  They also frequently require more life support through irrigation and fertilization then planted-in place systems.

Although modular system may look great on the day of installation, it is possible that they may not have the long-term sustainable performance that we like to develop at SYMBIOS. Furthermore, modular/containerized systems restrict the ability to develop aesthetic landscape designs that are seamless and dynamic. Although, planted in place type systems do require more patience as one must wait for the landscape to grow and mature, we feel it is well worth the wait. It is also far more rewarding and interesting to watch a living roof grow, develop and evolve over time.


11. What do these systems cost?

In our experience, every living roof job is unique. Each project has its own set of conditions and related construction expenses. Broad base unit pricing for such a highly specialize building system, such as vegetative roofs, is often misleading and results in incorrect financial assessments.

Call us with your project details. With our broad experience, we can provide you with an accurate and realistic notion of the associated costs.


12. Does the roof need an irrigation system?

Universally speaking – no. Here in the western United States, with our seasonal shifts of a wet and dry season, the answer is almost always YES.

However, you may choose not to irrigate if your roofscape vision is to be a native planting scheme and in harmony with the surrounding landscape.

In either case, it is an important feature to carefully plan and install correctly to your living roof. The performance and sustainable success of the roofscape frequently depends on it.

At SYMBIOS, we devise living roof systems that are water smart while providing the plants with adequate life giving water to stay healthy. Our irrigation systems use 1/20th of what a normal drip system uses and in combination with a drought tolerant planting palette, there is a minimal use of water. In addition, rainwater catchment and/or greywater systems can be integrated into the holistic design of the rooftop garden.


13. What is a GRP?

The definition of a GRP = Accredited Green Roof Professional.

The non-profit organization Green Roofs for Healthy Cities developed and oversees this professional accreditation process for the industry.

Companies and individuals who have successfully completed a multi-disciplinary exam encompassing five areas of concentration including pre-design, design, contract management, quality assurance and support, and maintenance receive this GRP designation.  GRP accreditation verifies that the individual has attained the level of interdisciplinary knowledge of best practices associated with the successful design, installation and maintenance of green roof systems.

Green Roofs for Healthy Cities organization in conjunction with industry experts from both the building science and the landscape arts have worked for over six years to develop training materials and a professional exam that covers best practices across the spectrum of professionals, in order to maintain the highest standards in this specialized multi-disciplinary field.

At SYMBIOS, we have completed this exam and are one of the few GRP in California.


14. What are the main benefits of hiring SYMBIOS?

SERVICE BASED:

As a service-based organization, we frequently specify the best features of several different products and combine them together to produce high performance systems designed for the long term.

ATTENTION TO DETAILS:

Construction detailing is our specialty. When it comes to living roof systems, SYMBIOS recognizes roof edge conditions, penetrations and flashing. These important aspects are behind-the-scene heroes of a successful installation and sustainable performance.

DESIGN + BUILD APPROACH:

As a design + build company, we can reduce the overall expense of the building process as compared to composing a team of different trades and consultants to execute your project.

LEED & BEYOND:

Although living roofs are inherently green by virtue of being alive, they may not always be ‘green’ by design. At SYMBIOS, we strive to develop systems that set a standard for being ecologically responsive from the roof membrane to the plants. We prefer and typically help specify roof membranes that are non-toxic, water based and highly durable over conventional waterproofing systems. We also specify drainage and retention mats composed primarily of recycled content materials and we use our own soil medium blend based on regional materials, which are organic.

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